1. Field of the Invention
This invention relates to a recording apparatus, and more particularly to a scanning mechanism having a carriage with a bearing portion at which the carriage is fitted on a guide shaft.
2. Description of the Related Art
The scanning mechanism having a carriage fitted on a guide shaft at a bearing portion thereof has been widely used in the recording apparatus such as printers, magnetic or optical disc or drum recorders and reproducers, particularly as the head scanning mechanism therefor.
By the way, as the structure of the bearing portion of the head carriage in the conventional mechanism of such kind, for the carriage is entirely made of plastic by molding, a hole through which a guide shaft is to pass is provided therein and is used to be a bearing portion without any alteration, or an oil-impregnated metal ring is equipped in this through-hole and is made the bearing portion.
However, the former means has a drawback in that the load due to the friction is large, and the variation of the load with movement of the carriage is so large that even when a servo system is used to control it, a stable movement is difficult, and the speed deviation becomes large. Meanwhile, the latter means has the one-sided contact of the metal. Therefore, as that portion is abrased, the play of the carriage becomes large. Hence, its drawback lies in terms of precision accuracy and durability.
Also, in the mechanism of this kind, to assure smoothness of its operation, or smooth scanning movement of the carriage, lubrication of its bearing portion must be needed. In the past, however, such lubrication has been made by human hand as necessity arises in such a way that a lubricant oil is poured to the bearing portion. Such a maintenance is very troublesome, and the possibility of occurrence of a malfunction due to failure to replenish oil was high.
Also, when in setting up such a scanning mechanism as has been described above, there have been employed first means wherein the support members for both ends of the guide shaft are formed separately from each other to a shape of slide plates, and after these have been mounted on both ends of the guide shaft, they are fixedly secured to the base plate, or second means wherein both sides of a base plate are bent to form support portions, and holes through which the guide shaft is to pass are bored in the support portions.
However, the former or first means though having a merit that the assembling operation is relatively easy, gives a drawback that because the support members are separate ones, assurance of the accuracy is difficult, so that later adjustment is needed, and position shifts due to vibrations are liable to occur. Meanwhile, in the latter or second means, the accuracy is ready to assure, but because the guide shaft must be inserted into the holes of the support portion, there is a drawback that the handling difficulty is large and the surface of the guide shaft when being inserted is apt to be scratched or damaged, which leads to vibrations and abrasion of the carriage.